[aussie_bloke]’s tin can TV is a mechanical television, a TV where the scanning lines of a CRT is replaced with a spinning disk with very small holes.(if you have a better analogy in this day of LCDs, tell us). Instead of the usual Nipkow disk, [aussie_bloke] used a small tin can.

The image displayed on this TV isn’t very large; there are only 30 scan lines and the pattern of the holes results in a display 10.5mm in width by 7.85mm high. Basically, this display is microscopic but it’s still very impressive.

Sure, you may not be able to sit your kids down in front of this can-powered TV and let them watch Yo Gabba Gabba for hours on end, but it’s more than enough to impress those technically minded kids.

You can check out a video of [aussie_bloke]’s can TV after the break. Thanks [gary] for sending this in.

Sorry, as an adult I probably could be impressed, but I’m not because I can see it. I do see some flickering, I just can’t make out the image. My eyes seem to be strained for some reason, so I check it another time

For some reason I love mechanical television (it’s just so low tech high tech I guess.) He could improve it (well sort of) by using a splitter from the MP3 player, make a stereo file, with one channel as video, one as audio, send the video channel to the LEDs and audio to a dollar store speaker, he could also get a bigger picture with a Fresnel lens in front of the picture display. John Logie Baird would be proud.

Of course they’re never going to increase the basic voice bandwidth, and it would make sense now to compress it with a codec, since nobody needs modems anymore. What use would it be? The voice telephone system’s not designed for sending narrow-band video, but dude! Internet! There y’go!

HAS to be done! You could do it with one string, possibly, depends on the audio response of a tightened string. Maybe it’d go into the ultrasonic, tho perhaps a single nylon wire would be better than organic, twisted-fibre string.

Then again, you could tighten the string with a lot of force at each end, then attach an audio transducer to the side of it rather than the end. Be interesting to see the bandwidth and freq response of tight string.

It is important to realise that whilst the resolution of mechanical television ACROSS the scan lines is (normally, but not always) low – eg 30 pixels in this instance, that the resolution along the scan lines is only limited by the size of the aperture in the direction of scan and the amount of light available, and is theoretically infinite. However, for transmission purposes square (or more often circular) apertures (or pixels if you prefer) are assumed. Since the bandwidth required for any (monochrome) television transmission is (number of lines) x (number of lines) x (aspect ratio) x (frames per second) / 2, then the bandwidth for this particular format is (30 x 30 x 4 / 3) / 2) = 7.5kHz – i.e. well within the audible range. hence ANY medium capable of carrying an audible signal up to 7.5 kHz will be able to transmit this particular video signal.

It should also be noted that the beauty of this particular implementation is it’s inherent simplicity. With very little extra effort (when compared to most other offerings to this site) full greyscale (i.e true B&W TV) and solid sync could be implemented, and, of course, with a CNC/Laser machine very precise accuracy can be obtained.

It should also be noted, particularly by RCA, that mechanical television is far from dead (e.g. DLPs, DynaScan http://www.dynascanusa.com/ds360.html, and countless other examples). CRTs were a useful, but momentary distraction ;-).

For those with a communications AND mechanical bent you can do far worse than take a look at this fascinating hobby. (http://www.nbtv.org/)

And now for the bad news…
The cellular system won’t allow 7.5 Khz bandwidth signals. Once you factor in Nyquist, you’re screwed. And that’s the good news.

The bad news: Land lines are increasingly following the lead of the cellular providers.
Cell phones often give you ~5khz bandwidth connections, and in a pinch even less.

English and spanish speakers can generally fill in missing information from context, and don’t complain too loudly when they can’t, so it behooves the cell firms to squeeze you into bits, as it were.

4.8 khz is about as bad as the big bad V has been able to descend without triggering a backlash of customer complaints. I they can compress your speech down to 4k, they just doubled their capacity.

I think at the moment that 3.1k is the lowest limit of usable speech, provided both speakers enunciate perfectly and the difference between tee and pee isn’t important.

There was a brief shining moment circa 1990~2002 when 12-16k was being compressed into 8khz, and with the right codecs Sprint could deliver very high quality audio in and out of legacy copper based systems. They made a big deal of it, and it sounded great.

However, the required last-mile technology is dissipating by the month, having been driven out of the market by Skype and voip.